Various epidemiologic and experimental in vivo and in vitro studies have suggested that polyphenols derived from fruits, vegetables and beverages might decrease the risk of developing lifestyle diseases, such as cardiovascular disorders and cancer. Apples are a major dietary source of polyphenols. Here we investigated the antitumor activity of apple polyphenols (APs) and procyanidins, namely condensed tannins, both in vitro and in vivo studies. APs and procyanidins inhibited the growth of transplanted B16 mouse melanoma cells and BALB-MC.E12 mouse mammary tumor cells, and increased the survival rate of the host mice-transplanted B16 cells. Among the APs, the apple procyanidins specifically, rather than other polyphenols such as chlorogenic acid, (-)-epicatechin, phloridzin and procyanidin B2, had a major effect on cell proliferation and induced apoptosis in vitro. The apple procyanidins increased mitochondrial membrane permeability and cytochrome c release from mitochondria and activated caspase-3 and caspase-9 within the tumor cells. In addition, we separated eight procyanidin fractions according to the degree of polymerization using normal-phase chromatography, and detected strong anti-tumor activity in the procyanidin pentamer and higher degree fractions. Our results indicate that the oral administration of apple procyanidins inhibits the proliferation of tumor cells by inducing apoptosis through the intrinsic mitochondrial pathway.

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Fish produce mucus substances as a defensive outer barrier against environmental xenobiotics and predators. Recently, we found a bioactive protein in the mucus layer of the flounder Platichthys stellatus, which showed antibacterial activity against Staphylococcus epidermidis, Staphylococcus aureus and methicillin‐resistant S. aureus. In this study, we isolated and identified the antibacterial protein from the mucus components of P. stellatus using a series of column chromatography steps. We then performed gel electrophoresis and cDNA cloning to characterize the protein. The antibacterial protein in the mucus had a molecular mass of approximately 52 kDa with an isoelectric point of 5.3, and cDNA sequencing showed that it corresponded completely with the peptide sequence of antibacterial protein from the gill. A BLAST search suggested that the cDNA encoded an antibacterial protein sharing identity with a number of l‐amino acid oxidases (LAAOs) and possessing several conserved motifs found in flavoproteins. RT‐PCR using a specific primer, and immunohistochemical analysis with anti‐LAAO IgG, demonstrated tissue‐specific expression and localization in the gill. Moreover, the anti‐LAAO IgG was able to neutralize the antibacterial activity of the protein against methicillin‐resistant S. aureus. Thus, we demonstrated that this antibacterial protein, identified from P. stellatus‐derived epidermal mucus, is a novel LAAO‐like protein with antibacterial activity, similar to snake LAAOs.

Amino acids exert many biological functions, serving as allosteric regulators and neurotransmitters, as constituents in proteins and as nutrients. GCN2-mediated phosphorylation of eukaryotic initiation factor 2 alpha (elF2α) restores homeostasis in response to amino acid starvation (AAS) through the inhibition of the general translation and upregulation of amino acid biosynthetic enzymes and transporters by activating the translation of Gcn4 and ATF4 in yeast and mammals, respectively. GCN1 is a GCN2-binding protein that possesses an RWD binding domain (RWDBD) in its C-terminus. In yeast, Gcn1 is essential for Gcn2 activation by AAS; however, the roles of GCN1 in mammals need to be established. Here, we revealed a novel role of GCN1 that does not depend on AAS by generating two Gcn1 mutant mouse lines: Gcn1-knockout mice (Gcn1 KO mice (Gcn1-/-)) and RWDBD-deleted mutant mice (Gcn1 ΔRWDBD mice). Both mutant mice showed growth retardation, which was not observed in the Gcn2 KO mice, such that the Gcn1 KO mice died at the intermediate stage of embryonic development because of severe growth retardation, while the Gcn1 ΔRWDBD embryos showed mild growth retardation and died soon after birth, most likely due to respiratory failure. Extension of pregnancy by 24 h through the administration of progesterone to the pregnant mothers rescued the expression of differentiation markers in the lungs and prevented lethality of the Gcn1 ΔRWDBD pups, indicating that perinatal lethality of the Gcn1 ΔRWDBD embryos was due to simple growth retardation. Similar to the yeast Gcn2/ Gcn1 system, AAS-or UV irradiation-induced elF2α phosphorylation was diminished in the Gcn1 ΔRWDBD mouse embryonic fibroblasts (MEFs), suggesting that GCN1 RWDBD is responsible for GCN2 activity. In addition, we found reduced cell proliferation and G2/M arrest accompanying a decrease in Cdk1 and Cyclin B1 in the Gcn1 ΔRWDBD MEFs. Our